Hibiscus (Hibiscus spp.) brighten landscapes, decks and patios with large, showy blue, pink, purple, red, white or yellow flowers from spring to fall. They range in height from 2-foot tall dwarfs[1] to trees that grow to a height of 10 feet (3 m) or more.[2] Hibiscus will grow well in USDA Hardiness Zones 4 to 10, [3] withstanding winter lows down to −30 °F (−34 °C),[4] while tropical hibiscus only grow well in Zones 9 to 12[5], where temperatures drop to only about 20 °F (−7 °C) in the winter. Tropical hibiscus can be grown in containers in cooler climates, however, and simply brought indoors when temperatures begin to drop down to 50 °F (10 °C). Hibiscus have some fairly specific requirements to flourish but their showy flowers are well worth it. A healthy, happy hibiscus will reach its mature height within two to three years with lush, healthy foliage and bloom profusely.

Steps

Part 1

Creating an Ideal Growing Environment

1

Place your hibiscus in a spot that gets at least six hours of direct sunlight a day. Though these plants will also grow in the light shade of very tall trees, they will grow more slowly and bloom less.

2

Hibiscus in containers should be outdoors in the summer and moved inside in the fall. Set your plant in its container outdoors in a bright, sunny area during the summer and move it to a bright location indoors in the fall, where it will be exposed to at least a few hours of direct sunlight each day.[6]

3

Maintain the right temperatures for indoor hibiscus. While tropical hibiscus are indoors during the fall and winter, temperatures should be kept at 70 to 75 °F (21 to 24 °C) during the day and 55 to 65 °F (13 to 18 °C) at night.

Part 2

Planting and Watering Your Hibiscus

1

Make soil mix with a lot of organic matter for your hibiscus. Mix a 3- to 6-inch layer of compost, well-aged cow manure, leaf mold or decomposed pine bark mulch into the top 10 to 12 inches (25.4 to 30.5 cm) of soil[7] with a rototiller to avoid creating pockets of organic matter that will interfere with water absorption.

2

Test the soil to determine its pH. Hibiscus require soil with a neutral to slightly alkaline pH of 7 to 7.2. If it is acidic with a pH of 6.8 or lower, sprinkle lime over the soil and till it in to bring the pH up.[8]

The amount of lime needed to raise the soil pH will depend on the texture of the soil. Loamy soil requires 1 pound of dolomitic lime to raise the pH of 25 square feet of soil from 6.5 to 7. Sandy soil requires less lime while clay soil requires more.[9]

3

Select a planting site where the hibiscus will be protected from strong wind. The wind can damage the leaves and break tender branches.[10]

4

Use potting soil with a high pH for hibiscus in containers. The potting soil should be made of 1 part topsoil, 1 part sphagnum peat moss and 1 part coarse sand, perlite or vermiculite.[11] The pH should be around 7 to 7.2. Check the label on the potting soil package to make sure it is within this range.

If the potting soil is acidic with a pH of 6 to 6.5, add 1/2 cup dolomitic lime per 2 gallons (7.6 L) of soil to raise the pH.

Do not use garden soil for planting hibiscus in containers. It will not drain properly and could contain fungal spores or bacteria that will infect the hibiscus.

5

Spread a 2- to 3-inch depth of organic mulch around the hibiscus to help keep the soil moist. However, be sure to keep the mulch a few inches away from the stems. Wet mulch pushed right up against the hibiscus stems will encourage bacterial blight and stem cankers.

6

Water your hibiscus as often as necessary to keep the soil lightly moist. Do this for the first year the hibiscus has been planted or potted, until it becomes well established.[12] Use a soaker hose or water the hibiscus by hand with a watering can to help prevent fungal and bacterial diseases that thrive on wet leaves. Give it 1 inch (2.5 cm) or 3 gallons (11.4 L) of water each time.

Measure how much water is given with a soaker hose by setting a 1-inch deep can next to the hibiscus before turning on the hose. When the can is full, the hibiscus has received 1 inch (2.5 cm) of water.

From the second year on, water the plant when the top 2 to 3 inches (5.1 to 7.6 cm) of soil becomes dry. Give it 2 inches (5.1 cm) or 6 gallons (22.7 L) of water each time.

7

Water hibiscus in a container when the top of the soil begins to dry during the spring, summer, and fall. Pour the water evenly over the soil until it drains freely from the bottom of the pot.

As the hibiscus will grow much slowly, if at all, during the winter, water it in the winter only when the potting soil is almost completely dry.[13] Keeping the soil too wet in the winter may result in root rot.

Hibiscus will drop their flower buds if they are watered too much or too little.

Part 3

Fertilizing and Pruning Your Hibiscus

1

Sprinkle a balanced, slow-release fertilizer with a 10-10-10 ratio over the soil around the hibiscus after planting. Use a slow-release fertilizer that will last for six months so the nutrients are available from mid-spring to early fall while the hibiscus is actively growing.[14]

Hibiscus planted in the garden should be given fertilizer formulated for garden plants while container-grown hibiscus should be given fertilizer formulated for houseplants. Garden fertilizer is too strong for container-grown plants and will burn their roots.

2

Give outdoor hibiscus about 1/4 cup of fertilizer and give container-grown plants only a few tablespoons of fertilizer. Recommended amounts vary, depending on how the fertilizer is formulated, so follow the manufacturer’s recommendations.

When hibiscus are not getting enough nitrogen, the leaves will turn yellow. You can sprinkle about 1/4 cup of granular 10-10-10 fertilizer over the soil and water it in to give the hibiscus a quick boost. Too much fertilizer will burn the roots and cause the edges of the leaves to turn dry and brown.

3

Do not give hibiscus fertilizer during the winter. They will not use it because they will be going through a dormant period and it could damage their roots.

4

Prune your hibiscus after they finish blooming. The entire shrub can be pruned back by up to one-third with hand pruners right after it blooms. This will encourage new branch growth and more flowers, as hibiscus bloom on new branch growth.[15]

Make the pruning cuts about 1⁄4 inch (0.6 cm) above a leaf. New branches will grow from just below where the old branch is cut.

Remove the fading flowers before they go to seed to encourage another flush of flowers.

Part 4

Fighting off Disease and Pests

1

Be wary of insects, splashing water, and wind. Hibiscus are susceptible to a number of diseases, including bacterial blight, leaf spots, and rust. Bacterial blights and leaf spots are spread by environmental factors like wind, splashing water, and insects. These diseases will cause yellow-edged tan or brown lesions on the leaves and flowers.[16] Rust, a fungal disease that causes an orange powdery substance to form on the leaves, is also spread the same way.[17]

2

Notice if the cool, damp weather is encouraging the growth of Botrytis blight. This is a gray mold that is similar to bacterial blight but is caused by a fungus.[18] It will appear as soft brown spots on the flowers, stems and leaves and causes mature flowers to rot quickly. Gray mold can also develop on the brown spots.

Another disease hibiscus is susceptible to is stem cankers, which are caused by fungi that infect hibiscus stems through wounds.[19] The cankers are usually brown but may be gray at the center.

3

Prune off any infected stems, leaves, or flowers. Pruning cuts should be made into healthy tissue about 1 inch beyond the infected area.

4

Disinfect your pruners and dry them between cuts to help prevent the spread of disease. You can disinfect your pruners by soaking them in disinfectant for a few minutes between cuts. Do not prune hibiscus with the pruners that are still wet with disinfectant as it causes damage to plant tissue.[20]

5

To help your plant recover from root rot, let the soil dry out before trying to water it again. Rather than discard a shrub with root rot, you can try to help it recover by pulling the mulch off the soil with a rake and carefully digging the soil away from the base of the shrub with a shovel. Make sure the soil dries out completely before watering it again.

Root rot occurs when the soil drains slowly and remains very wet for extended periods of time.[21] Hibiscus with root rot wilt and appear drought stressed because the roots are no longer able to supply the stems and leaves with moisture. The leaves often become dull green, yellow, red or burgundy. Hibiscus commonly die from this disease.

6

Prune out any branches affected with Verticillium wilt. Doing this, along with watering the diseased plant properly and giving it fertilizer each spring, will help it live longer. Make sure you disinfect your pruners between cuts of the branches.

Verticillium wilt has symptoms similar to root rot but they will appear on only one side of the shrub first.[22] The hibiscus may live for a few weeks or a few years but it will eventually die from this disease.

7

Re-plant the area with only Verticillium-resistant plants. The organism that causes Verticillium wilt lives in the soil even after the infected plant is removed. So, re plant and replace with a plant like:

Rose-of-Sharon (Hibiscus syriacus), which is a Verticillium-resistant hibiscus.[23] It grows well in Zones 5 to 9 where it can reach a height of 8 to 12 feet.

New Jersey tea shrubs (Ceanothus americanus)[24] are also a good option for re-planting in Verticillium-contaminated areas.[25]They produce showy, white flowers in late spring and early summer that attract hummingbirds and butterflies. New Jersey tea shrubs grow well in Zones 4 to 8, where they can reach a height of 3 to 4 feet.

8

Check your hibiscus for aphids, mites, mealybugs, scales insects, and whiteflies. All of these pests pierce the hibiscus leaves and suck out the plant’s juices. A healthy hibiscus can easily handle mild infestations of any of these pests with minimal damage.[26]

Aphids are often green or red but they can be almost any color. They are small, soft-bodied insects that move slowly and are often found on hibiscus stems and the undersides of leaves.[27]

Mites are tiny spider-type pests that are barely visible to the naked eye. They are often detected when their fine webbing is noticeable between the hibiscus’ leaves and stems. The leaves also develop a bronzy-looking blush and tiny dots.[28]

Mealybugs[29] and scale insects [30] are flat, round or oval pests that move slowly to a permanent place on the hibiscus when they are young and then attach themselves and lose their legs. Mealybugs are usually off-white and have a waxy coating that makes them look mealy. Scale insects are smooth and commonly tan, off-white or brown.

Whiteflies look like tiny white moths that fly up in a cloud when the hibiscus leaves are disturbed.[31]

9

Avoid pesticide treatments for pests. Besides being unnecessary, these treatments will kill beneficial insects like lady bird beetles, which are natural predators of these pests.[32] Lady beetles will usually bring an infestation under control when given an opportunity.

While lady bird beetles can be purchased and released into the garden, this is rarely effective. The lady bird beetles move on to other gardens very quickly. They ordinarily arrive naturally soon after the pests.

10

Prune out severely infested branches and put them in the trash. Disposing of them prevents the spread of more pests to other plants.

11

Hose down the hibiscus every other morning with a strong spray from the garden hose. The water will crush the pests and knock them off the shrub. It also makes the environment less than ideal for spider mites, which thrive in dry conditions.

12

Remove mealybugs and scale insects by rubbing them off with a thumbnail or a cotton ball dipped in Isopropyl rubbing alcohol. This will kill them and reduce the risk of spreading these pests to other plants.

13

Pick off any Japanese beetles and caterpillars by hand and drown them in a bucket of soapy water. Japanese beetles[33] and caterpillars[34] eat hibiscus leaves. Japanese beetles are medium-sized, oval, shiny green beetles. Caterpillars that attack hibiscus can be nearly any color or size. When you remove these pests by hand, drop them into a bucket of soapy water to drown them.

Wear gloves when removing caterpillars as some species will inflict a painful sting. Caterpillars are fairly easy to find at any time of the day.

Japanese beetles are easiest to remove early in the morning while they are sluggish.